Humidifying the cathode flow stream of a fuel cell system can require components that are costly, complex, consume an undesirable amount of space, and may be prone to inefficient or intermittent operation, depending on the application where the fuel cell is being used. This may be particularly true in vehicle applications, where available space is limited, and the fuel cell may be exposed to extreme ambient temperatures. For example, lines containing liquid water in such a system are susceptible to blockage issues in freezing conditions.